It is known that water dispersible polyester resins may be prepared by partially reacting trimellitic anhydride (TMA) with hydroxy terminated polyesters to produce polyesters containing sufficient carboxyl groups to make the polyester resin water soluble. This reaction is shown schematically below: ##STR1## The resulting polyester composition is poured into water which contains an amine dispersing agent, e.g. triethyl amine. However, in order to avoid rapid boiling and foaming of the water/amine solution, the temperature of the molten polyester must be less than about 200.degree.-220.degree. C. Since the temperature at which the polyester remains molten is a function of the resin's Tg and molecular weight, an effective upper limit is thus placed on them. Also, if the Tg and molecular weight of the polyester is too high, the polyester will solidify or become too viscous in the water/amine mixture (even if the water/amine mixture is kept close to boiling) before the polyester can be dispersed. The addition of solvent to the polyester before dispersing it, in an effort to obviate these problems, is undesirable since the flash point would be lowered and organic pollutants to the atmosphere increased when the product is ultimately dried.
Known water dispersible polyesters include those sold by Eastman Chemical Products, Inc. under the designations WD 3652, WD 9519, WJL 6342, FPY 6762 and MPS 7762. These polyesters are described as having molecular chains whose end groups are mostly primary hydroxyl groups, and which have sodium sulfonate groups positioned along the molecular chain at random intervals. These sodium sulfonate groups contribute to water dispersibility. Also available from Eastman is an air-drying water-reducible alkyd enamel prepared from a resin designated as WA-17-2T. This resin is prepared from 10.56 eq. of TMPD glycol (2,2,4-trimethyl-1,3-pentanediol), 8.12 eq. of pentaerythritol, 9.00 eq. of isophthalic acid, and 4.43 eq. of linoleic fatty acid. The resulting polymer is then reacted with 4.72 eq. of trimellitic anhydride. Other Eastman products containing water-reducible polyesters are WS-3-1C, WA-17-6C and WS-3-2C enamels. WS-3-1C enamel is prepared from a polyester made from 17.16 eq. of 1,4-cyclohexanedimethanol; 8.59 eq. of trimethylolpropane; 14.85 eq. of phthalic anhydride and 10.90 eq. of adipic acid. WA-17-6C enamel is prepared using a polyester made from 5.94 eq. of 1,4-cyclohexanedimethanol; 15.10 eq. pentaerythritol; 8.67 eq. isophthalic acid; 3.18 eq. benzoic acid and 3.65 eq. linoleic fatty acid. The resulting polymer is further reacted with 3.93 eq. of trimellitic anhydride. WS-3-2C enamel employs a polyester prepared from 7.12 eq. 1,4-cyclohexanedimethanol; 1.40 eq. trimethylolpropane; 4.17 eq. phthalic anhydride and 2.78 eq. adipic acid.
High molecular weight (i.e., over 4500 molecular weight) water reducible polyester resins have also been developed by Amoco Chemicals Corporation. One such resin is a polyester diol of isophthalic acid and glycol which is coupled with trimellitic anhydride. The prepolymer mole ratio of isophthalic acid to glycol must be at least 4:5 and near stoichiometric amounts of trimellitic anhydrides are used. A typical such resin is prepared from 120 moles of isophthalic acid (or an 85/15 isomer blend of isophthalic and terephthalic acids) and 140 moles of diethylene glycol. Twenty moles of the resulting prepolymer diol is then reacted with 21 mole of trimellitic anhydride. Similar Amoco polyesters are prepared by reacting the same ingredients described above, except that the glycol component contains 91 moles of diethylene glycol and 49 moles of 1,4-cyclohexanedimethanol.
U.S. Pat. No. 3,546,008, issued Dec. 8, 1970 to Shields, et al. discloses sizing compositions containing linear, water-dissipatable polyesters derived from at least one dicarboxylic acid component, at least one diol component (at least 20 mole percent of the diol component being a poly (ethylene glycol)), and a difunctional monomer containing a --SO.sub.2 M group attached to an aromatic nucleus, where M is hydrogen or a metal ion.
U.S. Pat. No. 3,563,942, issued on Feb. 16, 1971 to Helberger, discloses linear copolyester compositions which can be dispersed in aqueous mediums. Water dispersibility is gained by the addition to the copolyesters of the metal salt of a sulfonated aromatic compound.
U.S. Pat. No. 3,734,874, issued May 22, 1973 to Kibler, et al., discloses water-dissipatable, meltable polyesters and polyesteramides. A polyester said to be typical is composed of 80 mole parts of isophthalic acid, 10 mole parts of adipic acid, 10 mole parts of 5-sodiosulfoisophthalate, 20 mole parts of ethylene glycol and 80 mole parts diethylene glycol.
U.S. Pat. No. 4,148,779, issued Apr. 10, 1979 to Blockwell, et al., discloses water-dispersible dye/resin compositions which are solutions of disperse dyes in, for example, copolyesters of 5-sodiosulfoisophthalic acid optionally blended with aliphatic or cycloaliphatic dicarboxylic acids.
U.S. Pat. No. 4,391,934, issued July 5, 1983 to Lesley, et al., discloses dry textile warp size compositions containing a polyester in particulate form, a film former and, optionally, a lubricant. The preferred polyester resin is produced by reacting a glycol such as diethylene glycol with a dicarboxylic acid, e.g., isophthalic acid, and trimellitic anhydride.
U.S. Pat. No. 4,401,787, issued Aug. 30, 1983 to Chen, discloses polyester latex compositions which contain a polyester having from 0.5 to 5.0 mole percent dicarboxylic acid derived repeating units having a component selected from salts of alkali metal or ammonium iminodisulfonyl and alkali metal or ammonium sulfonate.
U.S. Pat. No. 4,493,872, issued Jan. 15, 1985 to Funderburk, et al., discloses a water dispersible copolyester made from 65 to 90 mole percent of isophthalic acid, 0 to 30 mole percent of at least one aliphatic dicarboxylic acid, 5 to 15 mole percent of at least one sulfomonomer containing an alkali metal sulfonate group attached to a dicarboxylic aromatic nucleus, and stoichiometric quantities of about 100 mole percent of at least one copolyerizable aliphatic or cycloaliphatic alkaline glycol having 2 to 11 carbon atoms.
U.S. Pat. No. 4,525,419, issued June 25, 1985 to Posey, et al., discloses a water dispersible copolyester which is the condensation product of 60 to 70 mole percent of terephthalic acid, 15 to 25 mole percent of at least one dicarboxylic acid, greater than 6 up to 15 mole percent of at least one sulfomonomer containing an alkali metal sulfonate group attached to a dicarboxylic aromatic nucleus, and stoichiometric quantities of at least one aliphatic or cycloaliphatic alkylene glycol having 2 to 11 atoms.